General term for the pass one gets to enter a secure filter, such as that of the interior cities of Nasheen or the Queen's palace. These may be physical organic paper passes or permanent semi-organic passes embedded beneath the skin. Keeping hold of either after it has been coded with your organic matter and logged in the city filtration system will generally ensure that the filter does not recognize you as a foreign organic threat.
From God's War:
“You keep hold of that,” she told him, “or the filter will eat you. No permanent residency, no permanent bio-pass into Mushtallah.” She flashed her teeth and gave Nyx a nod. “Good luck, my woman.”